Almost every time Microsoft deployed a new Windows 10 update, all of sudden we saw people complaining about their PC problem. One of those problems is a continuous loop when trying to shutdown the computer.
Instead of shutting down properly, it goes back to the welcome screen — a similar result when you restart the machine. There are lots of factors that may be causing this issue, but the following solution could help you.
1. Run the Start menu and find Choose a power plan.

2. On the left bar, click the Choose what the power buttons do.

3. Now, click the Change settings that are currently unavailable.

4. Remove the checkbox of Turn on fast startup (recommended) and click Save Changes.

After the new setting has been applied, your PC will likely shut down properly instead of restarting. Furthermore, I think you may need to know why this problem happens and how to prevent it in the future.
The problem might be caused by the hardware incompatibility with the Fast Startup configuration. In most cases, notebooks and laptops are the victims but are less common on desktop PCs. A bug in Windows 10 Update can also be responsible for the error.
Hence, please look up some news and forums about the latest Windows 10 update before installing the update. They usually provide a clear insight into what will happen after the update was installed and potential errors.